1. Field of the Invention
The present invention relates to respiratory interface devices for transporting a gas to and/or from an airway of a user which include, but are not limited to, a mask and a support assembly with a coupling assembly structured to couple the mask and support assembly and wherein the coupling assembly is further structured to limit the rotation of the mask relative to the support assembly.
2. Description of the Related Art
Masks for respiratory interface devices may include a relatively rigid faceplate and a softer patient contacting cushion. The mask is positioned over a user's nose and/or mouth and held in place by a support assembly. A support assembly includes at least one strap structured to extend about the user's head. The straps are coupled to the mask at a coupling. For example, the coupling between the mask and support assembly may be an elongated slot on the mask. The end of a flexible strap extends through, and is looped about, the slot. This type of coupling allows for limited rotation of the strap relative to the mask. The rotation is about an axis parallel to the slot. Another coupling assembly may be snaps mounted on the straps and mask. Such couplings allow for rotation about an axis extending perpendicular to the plane of the snap elements. Another type of coupling assembly is similar to a button. That is, a post with a cap extends from the mask and the strap includes a corresponding opening disposed at a vertex. That is, the strap is, for example, “V” shaped. The strap opening extends to the edge of the strap. A user then positions the post in the pocket defined by the V-shaped strap and allows the post to enter the opening. This coupling allows the mask to rotate about an axis parallel to the axis of the post.
With a slot coupling, the rotation of the mask relative to the straps is very limited. That is, the limited rotation about an axis parallel to the slot generally does not permit the mask to rotate relative to the support assembly. With snaps, each strap end in the support assembly may have a coupling. For example, if the support assembly has two straps that are coupled to each side of the mask, i.e. there are four coupling locations, one at each end of each strap, and each coupling location has a snap. In this configuration, the support assembly may become tangled when disengaged from the mask or otherwise be confusing to the user when attempting to couple each coupling at the proper location. Further, snaps are subject to free rotation. The post and V-shaped strap coupling may reduce the number of coupling points, but is also subject to free rotation.
Each of these types of couplings has disadvantages. That is, it is desirable to have a mask rotate within a limited range relative to the support assembly so that the mask consistently provides a tangent seat relative to the user's face. A strap and slot coupling does not allow for sufficient rotation. That is, if the configuration of the support assembly does not position the mask so as to provide a seat that is tangent relative to the user's face, the mask may not be rotated relative to the support assembly and the mask may not provide a complete seal against the user's face. Snaps and post couplings, on the other hand, allow free rotation meaning the mask may move beyond a configuration where the mask provides a seat that is tangent relative to the user's face. For example, a child may not like the straps rubbing their ears and reposition the straps closer to the top of their head. In this configuration, the mask is being pulled upwardly and may not provide a seat that is tangent relative to the user's face. In this configuration, the mask may not provide a complete seal against the user's face. Further, such free rotation allows the mask to rotate freely while not in use and may allow the support assembly to become tangled.